부력조정에 의한 외끌이기선저인망의 어획성능 개선

Abstract

This study was carried out to offer fundamental data for improving the fishing efficiency of the danish seine. The net height and the shape in the water were measured to analyze the efficiency of the existing danish seine. And then, an improved fishing gear was developed based on the results and was tested in the field. Measuring devices were attached on center of a ground rope and a head rope. The net height is the spread distance between the ground rope and the head rope, which was measured on the different ratio of buoyancy. The results are obtained as follows : 1. The net height estimated from the design plan of horizontal hanging ratio 0.40 in the existing danish seine A and B calculated the same value as 4.94m. 2. The net height of the existing danish seine A and B was 1.8m and 2.3m, which form 36.4% and 46.2% of the net height estimated from the design plan. 3. Water temperature of towing depth was about 13.2∼13.3℃ and surface temperature was 23.4∼28.2℃ 4. Buoyancy was changed as 79.5% and 96.2% relative to the sinking force in the existing danish seine. The net height of 79.5% was 3.95m which increased to 80% of the estimated net height. The other shows the same result with the first case. 5. It is not necessarily that the high buoyancy and sinking force ratio make the high net height, 80% is adequate as the buoyancy and sinking force ratio. 6. In case of the improved danish seine net, the mean of net height was about 5.0m. It means 58.3% of estimated net height 8.58m.